Simmons and Smith reported in 1958 the first cyclopropanation of alkenes using methylene iodide and zinc-copper couple in ether (Organic Reactions, vol. 20, 1, 1973). The reactive carbenoide was inferred to be iodomethylzinc iodide (ICH2ZnI) in Schlenc equilibrium with Zn(CH2I)2 and ZnI2. The reaction was found to be stereospecific namely the configuration of the olefin was retained in the product. The reaction required very long times (16-72 hours) and yields varied from 7% to 70%.
Ethylene was steadily generated during the reaction by dimerization of methylene iodide, its amount was inversely proportional to the amount of the cyclopropanation product. Chloroiodomethane reacted poorly and dibromomethane (DBM) was found unreactive (Simmons and Smith, J. Am. Chem. Soc., 81(16), 4256, 1959). The zinc-copper couple was prepared by melting zinc and copper powder followed by crushing the solid. Later researches simplified the procedure by in-situ treatment of granular zinc or zinc dust with copper or silver salts in acetic acid (Charette and Beauchemin, Organic Reactions, 58, chapter 1, pp. 1-415, 2001).
In view of the importance of the Simmons-Smith cycloproanation as synthetic tool, continuous efforts were made to replace the expensive methylene iodide by the much cheaper DBM and new conditions were sought to increase the reaction rate.
LeGoff (J. Org. Chem., 29(7), 2048, 1964) found that increased activation of granular zinc was achieved by addition of Cu(OAc)2.H2O in acetic acid. This couple allowed the use of DBM in the cyclopropanation of cyclohexene and cyclooctene in diethyl ether. The reaction times were 25-40 hours and the yields were 61% and 40% respectively. The yields were much lower than with methylene iodide and were not reproducible. Zinc dust-copper couple gave much lower yields.
Fabisch and Mitchell cyclopropanated simple olefins with DBM and zinc in tetrahydrofuran (THF) as a solvent. See J. Organometal. Chem., 269(3), 219, 1984. The reactions were carried out at 40° C. for 48 hours in absence of copper. The yields varied from 35% to 52.8%. Ethylene formation was observed. NMR analysis in perdeuterated THF was consistent with BrZnCH2Br. NMR showed that on standing BrZnCH2Br was converted to Zn(CH2Br)2 and ZnBr2.
Friedrich, Domek, and Pong improved significantly the DBM cyclopropanation of simple olefins by sonication of zinc dust in presence of 10 mol % CuCl in refluxing ether. See J. Org. Chem., 50(23), 464, 1985. After an induction period (0.5-1 hr) the reaction commenced and was over in 2-4 hours. The yields varied from 28-50%, where cyclohexene and cyclooctene gave 60% and 72% yield respectively.
These reaction conditions were applied to the synthesis of odorant II according to U.S. Pat. No. 5,929,291 (Bajgrowicz and Frater, 1999, Givaudan Roure Int).

The biscyclopropanated product II was obtained from the allylic alcohol I in 41% yield after continued sonication for 22 hours. To eliminate the induction period the reaction mixture containing DBM, zinc powder, and cuprous chloride in ether was sonicated for 30 minutes prior to the addition of I. The product exhibited sandalwood, fruity, creamy/milk-like, very long-lasting odor.
Friedrich, Lunetta, and Lewis reported (J. Org. Chem., 54(10), 2388, 1989) that sonication was not necessary when the zinc-copper couple was promoted by titanium tetrachloride (1.5-2 mole %). The reaction times were less than 2 hours and the yields were comparable to sonication. DBM and methylene iodide gave similar yields.
Friedrich and Lewis (J. Org. Chem., 55(8), 2491, 1990) found that the effect of addition of 2 mole % of acetyl chloride to zinc-copper couple is even stronger than titanium tetrachloride. Cyclopropanation of unactivated alkenes with DBM in refluxing ether in presence of 10 mole % copper chloride required 1-2 hours for completion. The yields varied from 33% to 76%. Cyclohexene and cyclooctene gave 61% and 88% yield respectively. Trimethylsillyl chloride was claimed to have similar promoting effect but no example was given.
The main disadvantage of Frederich procedures is the use of diethyl ether, an extremely flammable solvent (flash point of −45° C.) which could be explosive. Diethyl ether vapor is heavier than air thus accumulates and travels on ground and may be ignited by hot surfaces, static electricity or other ignition sources. Being sensitive to light and air it tends to form explosive peroxides. Taking account of its low boiling point (34.6° C.) and anesthetic properties its handling in production site requires very efficient heat exchangers to completely eliminate its release to the environment.
Zinc promoters such as chlorotrimethylsilane were later demonstrated to suppress the retarding effect of traces of lead in commercial zinc powder. Takai, Kakiuchi, and Utimoto. (J. Org. Chem., 59(10), 2671, 1994) demonstrated that a trace amount of lead found in pyrometallurgic zinc decreases the reactivity of zinc toward diiodomethane and iodoalkanes substantially, and this negative effect can be completely suppressed by the addition of a catalytic amount of Me3SiCl.

Thus, when methylene iodide was reacted with cycloctene (III) and lead-free (electrolytic) zinc dust in boiling ether for 8 hours, IV was obtained in 96% yield. NMR showed the presence of the carbenoid ICH2ZnI. However, when zinc dust containing 0.06 mole % of lead was used, the yield dropped to 2%, and no ICH2ZnI was detected. The addition of trimethylsilyl chloride (2 mole %) to zinc dust containing 0.5 mole % lead gave IV in 97% yield.
The promoted Friedrich cyclopropanation was applied to (E)-2-methyl-4-(2,2,3-trimethylcyclopent-3-enyl)but-2-en-1-ol (V) for the synthesis of [1-methyl-2-(1,2,2-trimethylbicyclo[3.1.0]hex-3-ylmethyl)cyclopropyl]methanol (VI, Javanol™), a fragrance ingredient. See U.S. Pat. No. 5,929,291.

Javanol™ was prepared in 48% yield. It exhibited sandalwood, very natural, floral, creamy, powdery, very strong and long-lasting odor.
The DBM-zinc cyclopropanation of V was shown (Bajgrowicz, Frank, and Frater, Helv. Chim. Acta, 81(7), 1349, 1998) to proceed in two steps, the faster step was the proximal cyclopropanation affording VII which was isolated in mere 14% yield. VII exhibits creamy, lactonic sandalwood odor.

The monocyclopropanated alcohol VII was later prepared by improved method based on magnesium carbenoid in 93% yield. Deprotonation of V with methylmagnesium chloride in THF was followed by reaction with DBM and tert-butylmagnesium chloride in diethyl ether at 10-20° C. See U.S. Pat. No. 8,450,533. Involvement of the magnesium carbenoid XMgCH2X as the active cyclopropanation agent was proposed (Brunner et al, J. Org. Chem. 73(19), 7543, 2008).
Javanol™ was also prepared by two consecutive cyclopropanations with DBM as solvent in high overall yield. U.S. Pat. No. 7,777,084 showed that triisobutyl-aluminium-FeCl3 catalyzed the distal cyclopropanation of V in presence of large excess of DBM as solvent at room temperature in 4 hours to afford VIII in quantitative yield. Aluminum carbenoid (iBu)2AlCH2Br was detected by NMR. After work-up, azeotropic drying and concentration of DBM down to 3 equivalents per 1 equivalent VIII, the magnesium carbenoid proximal cyclopropanation was applied to afford VI in 82% yield. See Brunner, Elmer, and Schroder, Eur. J. Org. Chem., 24, 4623, 2011.

The reactions exhibit high stereospecificity and high overall yields. Although DBM was used in very large excess it is recyclable. Unlike the previous methods the aqueous waste was free of zinc and copper salts. The disadvantages are the use of large excess of DBM of relatively low reactivity and large excess of expensive and pyrophoric triisobutylaluminum and t-Butyl magnesium chloride. The first step reactor throughput is only 4.3%. The aqueous waste contains large amounts of aluminum and magnesium hydroxides.
Rieke et al, (J. Org. Chem., 46(21), 4323, 1981) prepared highly active form of nanozinc by reducing zinc chloride with lithium in boiling dimethoxyethane. After exchanging the solvent with diethyl ether, cyclohexene was cyclopropanated with DBM by reflux for 6 hours to give bicyclo[4.1.0]heptane in 94% yield. The use of the highly corrosive lithium metal and its high sensitivity to water combined with the required solvent exchange to diethyl ether renders this method less attractive on industrial scale.
Sibille et al, (J. Org. Chem., 56(10), 3255, 1991) described the electrochemical cyclopropanation of allylic alcohols with DBM using zinc rod anode and carbon fiber cathode. The electrolysis was performed in a mixture of dichloromethane (DCM) and dimethylformamide (DMF) containing a mixture of Bu4NBr/Bu4NI and ZnBr2 generated by pre-electrolysis of 1,2-dibromoethane. The yields varied from 52% to 75%. Bromochloromethane (CBM) was used in the cyclopropanation of E-crotyl alcohol, E-cinamyl alcohol and 2-cyclohexen-1-ol in 54%, 59% and 75% yield respectively. Although cyclopropanation with the cheaper CBM was demonstrated for the first time, the need for dedicated electrochemical device capable of controlling the reaction heat greatly limits its application on industrial scale.
In spite of the research and development of the Simmons-Smith cyclopropanation process over the past 57 years, there is still a need for economic, rapid and safe cyclopropanation of alkenes in high yield.